Can I upgrade my iMac?

Is it possible to upgrade the memory from 8gb to 16gb, and video card from AMD 4850 to the latest version on my 2009/10 iMac? Running Snow Leopard and using boot camp for games on windows (COD etc) but some new game requirements (COD Ghosts) exceed my system ability. All advice appreciated.

You have a late 2009 27" iMac which uses the AMD 4850 card. Your iMac can be upgraded to 32 GB of memory. As for the graphics card, I don't know if on that particular model the GPU is on a removable card or whether it's surface mounted to the logic board. You'll need to check with iFixit.com to see if it's removable. And if it is, you need to do some searching to see it can be replaced with something more powerful. As to replacing it with the latest version of GPU used in current iMacs, the answer to that is no.